The invention relates to pulse generation, and more specifically to the high-speed charging of PFLs (Pulse Forming Lines) on a nanosecond (ns) or picosecond (ps) time scale. Historically pulse generation has taken place by the discharge of a charged PFL into a load. To generate very short pulses, ranging from nanoseconds to picoseconds, a fast switch is required. High pressure multichannel gas switches are capable of not only fast switching, they can handle higher voltages than almost any other type of switch including solid state. Switching speeds on the order of a few picoseconds are possible at several hundred kilovolts. In multichannel operation switch closure is of multiple channels producing a lower/overall switch impedance due to a large number of impedances in parallel per channel.
For multichannel operation it is necessary to "over volt" the switch by applying a rapidly changing voltage. Conventionally this has been done by using either a charging inductor or a charging resistor. However, when the charging time is on the order of nanoseconds, this is impractical because the impedance of components must be so low that there is insufficient isolation from the charging power source.
The rapid charging of a PFL, or the rapid application of a voltage to a switch, is attemped generally in the following U.S. Patents, the disclosures of which are incorporated herein by reference: U.S. Pat. No. 4,918,325 issued to Busby et al.; U.S. Pat. No. 4,912,369 issued to Moran et al.; U.S. Pat. No. 4,871,925 issued to Yamauchi et al.; and U.S. Pat. No. 4,477,746 issued to Piltch.
In Busby et al. a fast rise-time pulse is realized by a pulse generator that is electrically connected to a load by a coaxial transmission line with a polyvinyl chloride (PVC) dielectric flashover switch. The outer conductor of the transmission line is directly connected between the pulse generator and the load, while the inner conductor has two sections interconnected by the PVC switch. This system provides a current and voltage subnanosecond rise/time.
Moran et al. disclose a triggerable, spark gap switch for high voltage, high current, pulse power systems. Triggering is by an arc between one electrode and a trigger pin, with high repetition rates obtained by operating at voltages below the self-breakdown voltage of the switch.
Yamauchi et al. have a high-voltage pulse generator with a toroidal core switch of soft magnetic alloy ribbon. The alloy contains elements such as iron, copper, niobium, tantalum, molybdinum and titanium, and is at least fifty percent crystalline.
Piltch describes a high repetition rate switch for delivering short duration, high power electrical pulses by an electric field between electrodes near breakdown. A microwave generator connected to a waveguide produces pulses having sufficient energy to distort the electric field and cause breakdown between rail electrodes, which provide a large conduction area that reduces induction effects and minimizes electrode erosion.
Although the foregoing patents relate to pulse generation they do not facilitate energy flow. Accordingly it is an object of the invention to enhance pulse production using impedance matching techniques.
Another object of the invention to provide for rapid charging of PFLs (Pulse Forming Lines). A related object is to generate subnanosecond pulses using high-pressure gas switches, having low inductance with gas pressures up to 350 atmospheres or more, and high voltage capability and subnanosecond switching speed.
A further object of the invention is to increase the transfer efficiency of energy from a source to a PFL line. A related object is to realize energy transfer efficiencies approaching 100%.